Connector terminals are formed in plurality in the form of comb teeth arranged on a continuous band-like member having pilot holes and respectively provided with a pair of projections each having a minute area (e.g. 1 mm.sup.2 or less) at the end thereof which has to be plated. Various techniques have conventionally been employed for plating these minute portions. For instance, there have been known as typical plating devices such as the plating device which dips the whole end portion including the projections in the plating solution contained in a bath to conduct plating by controlling the liquid level to limit plating areas, or the injection plating device which shields the portions not to be plated with a mask and plates unmasked portions by jetting the plating solution on them (refer to Japanese patent application laid-open Nos. Sho 59-126784, Sho 57-161084, and Sho 55-83180).
All of the prior art plating devices have drawbacks, however. In the case of the former device, as the whole ends of a connector terminal including the projections which are the subject of plating are plated because a minute plating area is difficult to clearly define, the consumption of plating metal unavoidably increases. This presents a formidable problem when the plating metal is a precious metal such as gold. In the latter case, masking is extremely difficult especially when the subject area is not even but irregular, bent, or complicated. The plating area is not clearly defined by the device to thereby incapacitate sufficient reduction of metal consumption.
The present inventors proposed an improvement for brush plating method (Japanese patent application No. Sho 60-89016) wherein the surface of an insoluble anode is covered with a liquid retaining member which can constantly be supplied with plating solution, the plating device is configured to be in alignment with the interval between adjacent fork-like ends of a connector terminal so that the tip end portions of the connector terminal may be plated while moving in contact with the member retaining the plating solution. As the proposed technique is effective in plating only the portions of the connector terminal ends which actually contact with the member on the anode surface, it may be called a minute partial plating method as compared with the prior art methods which allow only partial plating, achieving a remarkable reduction in precious metal consumption and precise definition of plating area.
However, the amount of plating solution applied on the plating area and the scope (area) of the plating tend to be influenced by such factors of the solution retaining members as the material or conditions or retainability since the plating solution is supplied to the member directly when the member is dipped in or out of the solution. It has long been desired to have a plating device suitable for plating minute portions which is capable of specifying the plating areas precisely without being influenced by conditions of the retaining member, of maintaining such precisely specified areas for a long time, and of continuous plating.